JP5113026B2 - Front fork - Google Patents

Description

  The present invention relates to a front fork, and more particularly to an improvement in a front fork that is a hydraulic shock absorber that is mounted on the front wheel side of a two-wheeled vehicle and absorbs road surface vibrations that are input to the front wheel of the two-wheeled vehicle that is running.

  Conventionally, various proposals have been made for a front fork that is a hydraulic shock absorber that is mounted on the front wheel side of a two-wheeled vehicle and absorbs road surface vibrations that are input to the front wheel of a traveling two-wheeled vehicle.

  For example, in Patent Document 1, the vehicle body side tube and the wheel side tube are connected so as to be able to protrude and retract, and the suspension side spring urges the wheel side tube to protrude from the vehicle body side tube. A proposal with a damper is disclosed.

  In this proposal, the damper has compression side damping means that enables generation of compression side damping force during compression operation in the bottom end portion of the cylinder body coupled to the upper end portion of the vehicle body side tube. A rear air chamber defined by a free piston is provided on the downstream side.

  The free piston is moved forward so as to approach the compression side damping means by the urging force of the pressure spring, with the pressure spring consisting of a coil spring accommodated in the back side air chamber adjacent to the back surface. The cylinder slides in the bottom end of the cylinder body according to the oil amount change.

  Therefore, in this damper, when the amount of hydraulic oil in the damper is a predetermined amount, the cylinder body is applied by the urging force of the pressurizing spring adjacent to the back surface of the free piston and the reaction force in the rear air chamber. The pressure trend is maintained.

Then, for example, the amount of hydraulic oil in the damper reaches a predetermined amount due to expansion of the hydraulic oil due to an increase in the oil temperature in the damper, or when hydraulic oil from a reservoir outside the cylinder body flows into the damper during operation of the damper. If it exceeds the above condition, the cylinder moves backward so as to rise above a predetermined stroke, and so-called surplus hydraulic oil is released to return to the reservoir through the open communication hole at the bottom end of the cylinder body.
JP-A-6-147248 (see abstract, claim 1, claim 2 and FIG. 2)

  However, in the proposal disclosed in Patent Document 1 described above, the inside of the cylinder body can be maintained in a pressurized tendency by the urging force of the pressurizing spring adjacent to the back surface of the free piston and the reaction force in the rear side air chamber. Although there is basically no problem, it may be pointed out that there is a minor defect in its implementation.

  That is, the free piston accommodated in the cylinder body of the damper receives a reaction force in the back side air chamber defined by the free piston and is energized by the energizing force of the pressurizing spring adjacent to the back surface.

  The pressure spring is specifically composed of a coil spring. In the case of a coil spring, as is well known, an urging force is applied to a member to be urged adjacent to the distal end. There is a tendency to concentrate partially, making it difficult to act evenly in the circumferential direction.

  Therefore, the free piston urged by this coil spring tends to tilt when it slides, and develops a so-called twisting phenomenon called a galling to the part where the free piston is housed. It becomes easy.

  In order to make it difficult for the free piston to develop the sag phenomenon, for example, when the dimension in the sliding direction of the free piston is increased, the weight of the free piston is increased, and it is difficult to ensure preferable operating performance. Is invited.

  The present invention has been developed in view of such a current situation, and the object of the present invention is to guarantee a predetermined operating performance of a free piston that maintains a high pressure tendency in a cylinder body in an internal damper. It is to provide a front fork that is optimal for expecting improvement in its versatility.

  In order to achieve the above object, the configuration of the front fork according to the present invention basically includes a fork main body in which the upper end is coupled to the handle side and the front wheel is suspended at the lower end, and the front fork is housed in the fork main body. A damper that expands and contracts when the fork body expands and contracts, and the oil amount change in the damper is placed in the bottom end of the cylinder body that constitutes the damper behind the free piston of the storage. Compensated by the expansion and contraction of the defined back side air chamber, the back side air chamber is located inside the fork main body and the bottom end portion of the air chamber bordered by the oil level in the reservoir outside the damper When the free piston moves backward through a predetermined stroke by the hydraulic action from the cylinder body, the hydraulic pressure from the cylinder body is In the front fork that is released to the air chamber via the through hole, the gas in the atmospheric pressure or higher is supplied to the back air chamber and the air chamber in the reservoir communicating with the back air chamber via the communication hole. Suppose that is enclosed.

  Therefore, in the present invention, the change in the oil amount in the damper is compensated by the expansion and contraction of the rear air chamber defined by the free piston. By enclosing the gas at atmospheric pressure or higher in the chamber, the inside of the damper that starts the contraction operation can be maintained at a high pressure tendency, and a predetermined damping action can be surely realized.

  And in this invention, since the gas which becomes atmospheric pressure or more is enclosed in the back side air chamber, the arrangement of the pressurizing spring composed of the coil spring for energizing the free piston can be omitted, and the weight accordingly. Adopting a measure to increase the size in the sliding direction of the free piston, for example, in order to prevent the occurrence of the sag phenomenon in the free piston that is expressed because it has a coil spring as a pressure spring Without this, it is possible to avoid an increase in the weight which is also naughty.

  Further, in the present invention, the pressure of the sealed gas is set to be equal to or higher than the atmospheric pressure, so that the fork main body can be maintained in a predetermined extended state including the time of expansion and contraction. The suspension spring for urging the fork main body in the extending direction can be omitted, and the weight can be reduced.

  Hereinafter, the present invention will be described based on the illustrated embodiment. A front fork according to the present invention is mounted on the front wheel side of a two-wheeled vehicle and absorbs road surface vibrations inputted to the front wheel of the two-wheeled vehicle that is traveling. Functions as a shock absorber.

  As shown in FIG. 1, the front fork includes a fork main body F in which a front wheel (not shown) is suspended at a lower end while the upper end is coupled to a handle (not shown), The damper D has a damper D that is accommodated and expands and contracts when the fork main body F expands and contracts to perform a predetermined damping action.

  The fork main body F has a vehicle body side tube 1 whose upper end side is coupled to the handle side, and a wheel side tube 2 that suspends the upper end side of the vehicle body side tube 1 so that the upper end side can be projected and retracted and suspends the front wheel at the lower end portion. Do it.

  Incidentally, the fork main body F shown in the figure is set to an inverted type in which the vehicle body side tube 1 is an outer tube and the wheel side tube 2 is an inner tube. Although not shown, the vehicle body side tube 1 may be an upright type in which the vehicle body side tube 1 is an inner tube and the wheel side tube 2 is an outer tube.

  The fork main body F has a reservoir R that is inside and outside of the damper D. The reservoir R has an air chamber A with an oil level O as a boundary. In the present invention, when the fork main body F is in the most extended state, a gas that becomes atmospheric pressure or higher is enclosed.

  In the front fork of the present invention, the pressure of the gas sealed in the air chamber A in the fork main body F is set to be equal to or higher than the atmospheric pressure when the fork main body F is in the most extended state. This will be described in detail later.

  The damper D is set up as an inverted type in which the cylinder body 3 is an upper end side member and the rod body 4 is a lower end side member. Basically, the cylinder body 3 is connected to the vehicle body side tube 1. The rod body 4 is coupled to the wheel-side tube 2 and is erected on the shaft-core portion of the wheel-side tube 2.

  In the damper D, as shown in the drawing, specifically, the cylinder body 3 is integrally provided with a bottom end portion 31 serving as an upper end portion in the drawing. While 31 is suspended from the shaft core portion of the vehicle body side tube 1, a compression side damping means 5 and a free piston 6 described later are accommodated.

  That is, although not shown, the damper D has a piston body that is slidably received in the cylinder body 3 while being held at the tip portion that is the upper end portion of the rod body 4. A rod side chamber and a piston side chamber, and a damping means for allowing mutual communication between the rod side chamber and the piston side chamber, and a predetermined damping action is realized when hydraulic oil passes through the damping means. .

  And in this damper D, the amount of hydraulic oil corresponding to the intrusion rod volume which becomes redundant in the piston side chamber during the contraction operation in which the rod body 4 becomes immersed in the cylinder body 3 flows out to the reservoir R side. Let

  In addition, in the damper D, contrary to the above, the operation corresponding to the retraction rod volume integral which is insufficient in the piston side chamber at the time of the expansion operation in which the rod body 4 protrudes from the cylinder body 3. Oil is replenished from the reservoir R side.

  The compression side damping means 5 which will be described later embodies the damping action when the oil amount changes in the damper D when the damper D expands and contracts, and also compensates for the oil amount change in the damper D. This is also the expansion / contraction of the free piston 6, which will be described later, that is, the back side air chamber A1 defined behind the free piston 6.

  That is, as described above, in this damper D, the cylinder body 3 has a bottom end portion 31 as shown in FIG. It has a compression side damping means 5 corresponding to a valve.

  Here, the bottom end portion 31 in the cylinder body 3 will be described briefly. The bottom end portion 31 is formed in a cylindrical shape having a larger diameter than the cylinder body 3, and the lower end connecting portion 31 a is an open end in the cylinder body 3. The lock nut 32 is screwed on the outer periphery of the portion 3a.

  The bottom end portion 31 is screwed at the upper end connecting portion 31 b to the inner periphery of the upper end portion of the vehicle body side tube 1 so that the bottom end portion 31 is disposed on the shaft core portion of the vehicle body side tube 1. I have to.

  The bottom end portion 31 includes a main body portion 31c that houses the compression side damping means 5 and slides the free piston 6, and a diameter-enlarged portion that continues to the main body portion 31c via a tapered portion 31d. 31e, and the diameter-expanded portion 31e has a communication hole 31f that allows communication inside and outside the case portion 31.

  When the bottom end portion 31 of the cylinder body 3 is formed as described above, the compression side damping means 5 has the inside of the bottom end portion 31 inside the cylinder body 3, that is, the piston side chamber side described above, and the reservoir. While defining on the R side, that is, on the free piston 6 side described later, mutual communication between the piston side chamber side and the free piston 6 side is allowed.

  The pressure-side damping means 5 includes, for example, an annular leaf valve 51. In particular, when the piston-side chamber side is communicated with the free piston 6 side, a predetermined damping action is performed by the annular leaf valve 51, that is, Realizes the compression-side damping action.

  Incidentally, the compression side attenuating means 5 is held at the tip portion facing the inside of the cylinder body 3 in the center rod 7 suspended from the shaft core portion of the vehicle body side tube 1 as shown in the figure.

  The center rod 7 is basically suspended from the shaft core portion of the cap 11 that closes the upper end opening of the vehicle body side tube 1 and is present at the shaft core portion of the bottom end portion 31. By the way, the cap 11 is screwed onto the inner periphery of the upper end connecting portion 31b at the bottom end portion 31 described above, and this cap 11 has an air valve V that allows gas to be supplied to and discharged from the rear side air chamber A1 described later. Do it.

  On the other hand, in the damper D, the free piston 6 accommodated in the bottom end portion 31, particularly in the main body portion 31 c at the bottom end portion 31 so as to be in series with the compression side damping means 5. The free piston 6 is slidable. The free piston 6 includes a pressure receiving surface side oil chamber R1 in the bottom end portion 31 of the main body 61 on the pressure side damping means 5 side, and a reservoir R side, that is, the above-described rear side air chamber. It is defined as A1.

  The free piston 6 is in sliding contact with the inner periphery of the main body 31c while having the seal 62 and the bush 63 on the outer periphery of the main body 61, and the outer periphery of the center rod 7 while having the check seal 64 on the inner periphery. Is slidably contacted, that is, slidably interposed.

  Further, the free piston 6 moves backward in the bottom end portion 31 so as to rise in the drawing, and particularly when the main body 61 reaches the inside of the tapered portion 31d, the outer periphery of the free piston 6 And the inner periphery of the taper portion 31d, a gap appears, and the passage to the reservoir R through the communication hole 31f inside the main body portion 31c is allowed through the gap.

  Therefore, in this free piston 6, when the amount of hydraulic oil in the damper D is at a predetermined amount, the reaction force in the rear air chamber A1 defined behind the free piston 6 causes the inside of the cylinder body 3 to move. Maintain a pressure trend.

  In the free piston 6, for example, the expansion of the hydraulic oil due to an increase in the oil temperature in the damper D or the hydraulic oil from the reservoir R outside the cylinder body 3 is caused by the damper D during the operation of the damper D. When the amount of hydraulic oil in the damper D exceeds a predetermined amount, for example, by flowing into the cylinder, the hydraulic oil moves backward so as to rise above a predetermined stroke, and the open end communicating hole 31f is formed in the bottom end 31 of the cylinder body 3. In other words, excess hydraulic oil is released so as to return to the reservoir R.

  By the way, the above-described free piston 6 has a bottom end portion 31 in the downstream side of the pressure-side damping means 5 which is the so-called upstream side of the free piston 6 and a back side air chamber A1 which is the back side of the free piston 6. It is defined in.

  At this time, in the present invention, the rear side air chamber A1 does not have a pressurizing spring, and when the damper D is in the most extended state, it is equal to or higher than atmospheric pressure, that is, for example, approximately 0.3 atm. The above gas is sealed.

  That is, as disclosed in the above-mentioned Patent Document 1 and as disclosed in Japanese Patent Application Laid-Open No. 2005-30534, this type of free piston has a coil spring as a biasing means behind. It is normal to have a pressure spring (39 or 4).

  Therefore, even in the present invention, it can be said that it is normal to have a pressure spring made of a coil spring behind the free piston 6, but as described above, in the case of a coil spring, the cover adjacent to the tip is roughly. It is difficult to apply an urging force to the urging member evenly in the circumferential direction of the coil spring, and when the urged member is the free piston 6, the free piston 6 is distorted. There is a harmful effect that makes it easier.

  Therefore, in the present invention, when the free piston 6 is urged from the back, the reaction force in the back side air chamber A1, that is, the air spring force is used without using the pressurizing spring. The occurrence of the wobbling phenomenon in the free piston 6 due to the use of the pressure spring is blocked in advance.

  And in this invention, since the expression of the wobbling phenomenon in the free piston 6 can be prevented, in order to stabilize the slidability of the free piston 6, the dimension in the sliding direction of the free piston 6 is formed large. It is possible to prevent the weight from increasing.

  Therefore, in this front fork, it is possible to maintain the inside of the damper D in a pressurized state even at the maximum extension, and therefore, from the beginning when the damper D starts contracting operation from the maximum extension state. It enables the expression of a predetermined compression side damping action.

  On the other hand, in the front fork, when the fork main body F is in the maximum extension state, a gas that is equal to or higher than the atmospheric pressure is sealed, so that the fork main body F is expanded by the reaction force that the gas expands, that is, The front fork can be urged in the extending direction. Therefore, in the conventional front fork disclosed in Patent Document 1, for example, the suspension spring arranged in the fork main body F is naturally arranged. The setting can be omitted.

  Incidentally, the applicant confirmed that when the damper D having the cylinder body 3 having a diameter of about 25 mm and a length of 30 mm is in the most extended state, the pressure in the back side air chamber A1 is almost equal to or higher than the atmospheric pressure. When the gas of 3 MPa is sealed, the internal pressure of the damper D in the most contracted state becomes approximately 2.0 MPa, so that the fork main body F can be urged in the extending direction without having a suspension spring. Become.

  And in this invention, since back side air chamber A1 has air valve V, the air pressure enclosed in back side air chamber A1 using this air valve V can be made variable, and the optimal enclosed air pressure. Can be selected.

  Further, when the suspension spring is omitted due to the air pressure in the rear side air chamber A1, the rear side air is contracted when 1/3 of the stroke from the maximum extension state to the maximum contraction state of the damper D is operated. A balance spring that cancels the air spring force generated by the chamber A1 may be provided in parallel with the extended spring in the damper D.

  As described above, when the free piston 6 moves backward in the bottom end portion 31 so as to rise in the drawing and reaches the tapered portion 31d continuing to the main body portion 31c, the free piston 6 is located in the lower portion in the drawing. The pressure receiving surface side oil chamber R1 crosses the outer periphery of the free piston 6 and communicates with the communication hole 31f. Considering the function of the free piston 6, however, instead of this, the inner periphery of the free piston 6 is not shown. On the other hand, a relief flow path communicating with the communication hole 31f may appear between the inner periphery of the free piston 6 and the outer periphery of the center rod 7 facing the free piston 6, and in this case, the bottom end portion This is advantageous in that the formation of the tapered portion 31d with respect to 31 can be omitted.

1 is a front view showing a front fork partially broken according to an embodiment of the present invention. FIG. 2 is a partial half-longitudinal longitudinal sectional view showing an upper end side portion of the front fork of FIG. 1 in an enlarged manner.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Car body side tube 2 Wheel side tube 3 Cylinder body 3a Open end part 4 Rod body 5 Pressure side damping means 6 Free piston 7 Center rod 11 Cap 31 Bottom end part 31a Lower end connection part 31b Upper end connection part 31c Main body part 31d Taper part 31e Expansion Diameter portion 31f Communication hole 32 Rod nut 51 Annular leaf valve 61 Seal 62 Bush 63 Check seal A Air chamber A1 Back side air chamber D Damper F Fork main body R Reservoir V Air valve

Claims (4)

A fork main body having a front end suspended at the lower end while the upper end side is coupled to the handle side, and a damper which is accommodated in the fork main body and expands and contracts when the fork main body expands and contracts to perform a predetermined damping action. The change in the amount of oil in the damper is compensated by the expansion and contraction of the back side air chamber defined behind the free piston accommodated in the bottom end of the cylinder body constituting the damper, and this back side air chamber is The free piston communicates from the cylinder body to the air chamber inside the main body and bordered by the oil level in the reservoir outside the damper via the open end communicating hole. In the front fork in which the hydraulic pressure from the cylinder body is released to the air chamber through the communication hole when a predetermined stroke is retracted by hydraulic action, the rear air chamber is Beauty front fork, characterized in that formed by sealing the atmospheric pressure or more gases to the gas chamber in the reservoir which communicates through the communication hole behind this side air chamber. A bottom end portion of the cylinder body is suspended from a shaft core portion of a vehicle body side tube constituting the fork main body, and the free piston is slidably received in the bottom end portion. The front fork according to claim 1, wherein the communication hole is opened at an end. The damper has a compression side damping means in the bottom end portion of the cylinder body, and the pressure side damping means is a tip of the center rod that is suspended from the shaft core portion of the vehicle body side tube and faces the cylinder body. The free piston is slidably contacted with the center rod so that the free piston is allowed to communicate with the upstream side of the free piston in the cylinder body. The front fork according to 2. The cap member that closes the upper end of the vehicle body side tube constituting the fork main body has an air valve that enables gas to be supplied to and discharged from the rear side air chamber. The front fork described in.

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